Color filters are critical parts of a liquid crystal display (LCD) or an image sensor. Color filter arrays consisting of a plurality of R, B, G color filter elements are employed in combination with sensors to define color images or in combination with display devices to permit color images to be viewed.
A common approach for producing color filter arrays has been taught by using organic dyes embedded in a layer which has been patterned by various techniques to render the appropriate filter pattern. However, it is hard and time consuming to allow the organic dyes for altering the spectral characteristics. Furthermore, the organic dyes may be subject to fading with time especially under harsh environmental operating conditions, such as high light levels of ultra violet (UV), etc. Currently, dichroic films are thus adopted by the art to take the place of the traditional dyes.
Typically, the color filter arrays consisting of the patterned dichroic films may be fabricated by steps as follows: A patterned photo-resist layer is formed on a substrate; a dichroic film is then formed on the substrate and the patterned photo-resist layer by a film deposition process; and a lift off process is subsequently performed to strip off the patterned photo-resist layer, so as to define the appropriate filter pattern.
However, the dichroic films based color filter arrays still have some drawbacks, for example, photo-resist reflow may occur during the film deposition process due to the low glass transition temperature (Tg) of the photo-resist layer. Thus, it is unlikely to obtain a filter pattern having a clear, sharp and steep pattern profile after the reflowed photo-resist layer is stripped off. As a result, the yield of the color filter arrays could be adversely affected.
Therefore, there is a need of providing an advanced method for fabricating a patterned dichroic film to obviate the drawbacks and problems encountered from the prior art.